1. Field of the Invention
The present invention relates to a fluorescent lamp, and more particularly, to an external electrode fluorescent lamp (EEFL), a method of fabricating the same and a liquid crystal display device having the same that have a reduced non-fluorescent region.
2. Discussion of the Related Art
As the information age progresses, flat panel display (FPD) devices having light weight, thin profile, and low power consumption characteristics are being developed and commonly used as substitutes for cathode ray tube (CRT) devices. Generally, display devices may be classified according to their ability for self-emission, and the classification may include emissive display devices and non-emissive display devices. The emissive display devices display images by taking advantage of their ability to self-emit light, and the non-emissive display devices require a light source since they do not emit light by themselves. For example, plasma display panel (PDP) devices, field emission display (FED) devices, and electroluminescent display (ELD) devices are emissive display devices. Liquid crystal display (LCD) devices, which may be categorized as non-emissive display devices, are commonly used in notebook and desktop computers because of their high resolution, capability of displaying color images, and high quality image display.
An LCD module of the LCD device includes an LCD panel for displaying images and a backlight unit for supplying light to the LCD panel. The LCD panel includes two substrates facing and spaced apart from each other, and a liquid crystal layer interposed therebetween. Liquid crystal molecules of the liquid crystal layer have a dielectric constant and refractive index anisotropic characteristics due to their long, thin shape. In addition, two electric field generating electrodes are formed on the two substrates, respectively. Accordingly, an orientation alignment of the liquid crystal molecules can be controlled by supplying a voltage to the two electric field generating electrodes, thereby changing transmittance of the LCD panel based on polarization properties of the liquid crystal molecules. However, since the LCD panel is a non-emissive-type display device, an additional light source is required. Thus, the backlight unit is disposed under the LCD panel. In particular, the LCD panel displays images using light produced by the backlight unit.
In general, backlight units may be classified into edge-type and direct-type according to the disposition of the light source. As display areas of the LCD devices become increasingly large, direct-type backlight units including a plurality of light sources have become commonly used to provide high brightness.
A fluorescent lamp, the light source of the backlight unit, includes a cold cathode fluorescent lamp (CCFL). A CCFL includes an external electrode that extends from an end portion of the glass tube. However, with respect to a large size LCD panel, the CCFL in the edge-type backlight unit fails to provide adequate brightness because it becomes difficult to evenly distribute light to the large size LCD panel. Meanwhile, the CCFL in the direct-type is connected as a parallel arrangement, but the CCFL is not driven using one inverter. Thus, the number of the CCFL limits a proper brightness of the LCD panel. Therefore, a reflector having a predetermined configuration is necessary, and the distance between the diffusion plate and the CCFL is greater for obtaining a uniform brightness. Consequently, a thickness of the LCD panel undesirably increases.
Accordingly, with respect to a large size LCD panel, which demands high brightness and high efficiency, an external electrode fluorescent lamp (EEFL) is suggested, which can provide a long life and a light weight for the LCD panel. The EEFL can be a belt type, a cap type or an expanded type. In an expanded type EEFL, both end portions of the glass tube thereof are swelled out.
FIG. 1 is a schematic view illustrating an EEFL according to the related art. In FIG. 1, a glass tube 14 includes a fluorescent region FR and a non-fluorescent region NFR at a periphery of the fluorescent region FR. In contrast to a CCFL, which includes an external electrode that extends from an end portion of a glass tube, an external electrode 13 is formed on an outer surface of the glass tube 14 in the non-fluorescent region NFR. The external electrode 13 includes a conductive material having a low electric resistance. Although not shown, another external electrode 13 is formed at another end of the glass tube 14, such that the external electrodes 13 respectively function as an anode and a cathode.
FIG. 2 is a schematic cross-sectional view illustrating an LCD device including the EEFL shown in FIG. 1. As shown in FIG. 2, an liquid crystal display (LCD) device includes a liquid crystal display (LCD) panel 18. The LCD panel 18 includes a display region DR and a non-display region NDR, such as a bezel region, at a periphery of the display region DR. The LCD device also includes a lamp-fixing unit 17 connecting the LCD panel 18 and an EEFL 15. In particular, the EEFL 15 is secured by the lamp-fixing unit 17. The EEFL 15 includes a fluorescent region FR and a non-fluorescent region NFR at a periphery of the fluorescent region FR. Specifically, an overlapping portion OLR corresponds to a portion of the non-fluorescent region NFR of the EEFL 15 overlapping the display region DR of the LCD panel 18.
The overlapping region OLR between the non-fluorescent region NFR and the display region DR has a much lower brightness than the center of the display region DR due to the external electrode 13. In particular, the longer the external electrode 13 is, the larger the overlapping region OLR becomes, thereby reducing a regular luminous portion of the display region DR. As a result, the liquid crystal display device according to the related art does not provide uniform brightness, thereby deteriorating image quality.